TTRE: A new type of error to evaluate the accuracy of a paired-point rigid registration

Target registration error (TRE) is widely adopted to evaluate the accuracy of a paired-point rigid registration (PPRR). However, TRE is defined in such a way that target localization error (TLE) is not considered. In this paper, we first propose a new type of error that is referred to as total target registration error (TTRE). The statistical model of TTRE is derived that we take the TLE in two spaces to be registered into consideration. Results in the first simulation show that the developed model can accurately estimate the simulated TTRE root-mean-square (RMS) (RMS percent differences|| <; 1.5% ± 2%) in all test cases. When all elements of diagonal FLE and TLE covariance matrices are independently generated from a uniform distribution that spans from 0 to 1mm and the number of fiducials N ≥ 6, the mean and covariance matrix of TTRE are well modelled. We have also theoretically proved and validated through the second simulation that TTRE and fiducial registration error (FRE) are uncorrelated (correlation coefficient (CC) <; 0.1). Finally, TTRE and TRE were found to exhibit a low correlation (0.37 <; CC <; 0.46).